1. Field of the Invention
The present invention relates to a proportional solenoid valve in which a valve element is displaced by applying a current to a solenoid to obtain an output pressure which is proportional to the value of the applied current.
2. Description of the Related Art
In a conventional proportional solenoid valve, a valve element is displaced while being guided by a valve guide portion that is provided for a solenoid main body. Also, a valve seat member having a seat portion, which the valve element is brought into and out of contact with, is fixed to a housing coupled to the solenoid main body (see JP 2002-525524 A, for instance).
As described above, in the conventional proportional solenoid valve, the valve element is provided on the solenoid main body side and the seat portion is provided on the housing side, so that an error occurs in the coupling position of the housing with reference to the solenoid main body due to machining tolerances of the coupling portion between the solenoid main body and the housing. As a result, coaxiality between the valve element and the seat portion is lowered. Also, when the housing is welded to the solenoid main body, a distortion occurs in the housing, which causes a positional shift of the valve element with reference to the seat portion. The influence of the distortion varies depending on welding conditions such as the amount of welding heat and a welding range, so that it is difficult to manage the positional shift. Further, when the housing is made of a resin, the positional shift of the valve element with reference to the seat portion occurs also due to deformation of the housing resulting from operating temperature.